I will give you the best advice that you won't follow:
Approach girls.
That's it.
You will literally learn this as you go. You'll understand how to have a conversation, not be outcome dependent, read nonverbal cues, handle rejection, escalation, etc. The most progress I ever made on this front was when I would use my vacation time at the beach to approach ANY girl I thought was hot to hit on her. Use canned lines to start with, it doesn't matter. You're going to get rejected a LOT, and then eventually you won't care, and then you'll get rejected LESS.
Also yeah go the gym.